Re: BUG: KASAN: use-after-free in usb_hcd_unlink_urb+0x5f/0x170 drivers/usb/core/hcd.c

[Greg KH]

On Mon, Mar 23, 2020 at 02:16:43AM -0400, Kyungtae Kim wrote:
> We report a bug (in linux-5.5.11) found by FuzzUSB (a modified version
> of syzkaller)
> 
> In function usb_hcd_unlink_urb (driver/usb/core/hcd.c:1607), it tries to
> read "urb->use_count". But it seems the instance "urb" was
> already freed (right after urb->dev at line 1597) by the function "urb_destroy"
> in a different thread, which caused memory access violation.
> To solve, it may need to check if urb is valid before urb->use_count,
> to avoid such freed memory access.

Can you send a patch for this?  Do you have a reproducer?

thanks,

greg k-h